Recently, requirements to further narrow display devices have been increased in the technical field of display devices such as liquid crystal display devices and organic electroluminescent (EL) display devices. In addition, flexible display devices capable of bending by being formed of substrates having flexibility have been developed.
Such a display device comprises a pad connected to external circuits and the like in a non-display area around a display area and supplied with a voltage, conductive lines connected to the pad, and the like to supply the voltage to pixels. To narrow the display device, the display device is accommodated in an electronic device and the like with the substrate bent such that a pad is disposed on a back surface of the substrate. A technology of forming a hole penetrating at least one of insulating films under the conductive lines in order to suppress break of the conductive lines in the bent area has been well known.